Ammonium sulfite monohydrate is widely used in the photography industry as a fixing agent to remove unexposed silver halides from photographic films and papers. It helps stabilize images and prevent further exposure to light. In the textile industry, it serves as a reducing agent in dyeing processes, aiding in the fixation of dyes onto fabrics. It is also employed in water treatment as an oxygen scavenger, preventing corrosion in boilers and pipelines by removing dissolved oxygen. Additionally, it finds application in the food industry as a preservative to maintain the freshness and color of certain products. In chemical synthesis, it acts as a reagent for producing other sulfur-containing compounds.